One type of assembled commutator comprises a pre-formed plastic base on which a plurality of segments is mounted. The segments are formed locked to the base, for example by providing tongues on the segments which are received in recesses in the base. Each segment has a connector portion which extends radially outwards and has a U-shaped portion supported by a collar on the base. To connect an armature coil to the segment, the coil wire is wrapped into the base of the U-shape which is then collapsed onto the wire and heated in a hot forging or resistance welding process to burn off the insulation covering on the wire and form an electrical and mechanical connection with the wire. A first electrode is brought down onto the U-shaped part and a second bears on the brush contacting portion. This may result in distortion of the base in the region of the brush contacting portions.